I am getting a DC 4-2-1 1 Piece Header. Should I run a 2.5 Carsound HiFlow Cat and 2.5 Magnaflow Resonator and 2.5 Magnaflow or Flowmaster Muffler and 2.5 inch piping?

Or instead of 2.5 inch piping and all those parts, run 2.25?

Also, how bad will it be if I don't put in a Resonator and just use the cat and muffler?

 

im running 2.25 from the header to muffler i got a es canister sounds raspy so im getting a cat installed soon. but i would go with 2.25.

 

Put in a resonator in please.

I ran a full 2.25 piping without a resonator from the cat back to a Twin Loop and it was loud as hell. Went back to the shop and got a resonator install 1 hour after.